> Also, I don't even use my ISPs name servers, I use Cloudflare or Google, so I don't think it's that unless the ISP is somehow munging the packet in transit, which I suppose is possible.
That's exactly the problem. You send out two v4 DNS UDP packets one after another (one for A, another for AAAA), both go via your ISPs CGNAT, the CGNAT gets confused, one of the packets gets dropped. I've seen this exact behavior when talking to 8.8.8.8 on Orange in Poland (and they do DS-Lite). It didn't occur with the ISP's DNS, because a) they were also on v6 b) they weren't getting CGNATed.
> But my point is, I shouldn't have to be a network engineer to make v6 work. I should be able to turn on my computer and just have it work.
By disabling IPv6 you're letting shit ISPs get away with this. Your ability to debug this and to figure out it's the ISP's issue should be used to voice your concerns, and not just let this slide.
That's exactly the problem. You send out two v4 DNS UDP packets one after another (one for A, another for AAAA), both go via your ISPs CGNAT, the CGNAT gets confused, one of the packets gets dropped. I've seen this exact behavior when talking to 8.8.8.8 on Orange in Poland (and they do DS-Lite). It didn't occur with the ISP's DNS, because a) they were also on v6 b) they weren't getting CGNATed.
> But my point is, I shouldn't have to be a network engineer to make v6 work. I should be able to turn on my computer and just have it work.
By disabling IPv6 you're letting shit ISPs get away with this. Your ability to debug this and to figure out it's the ISP's issue should be used to voice your concerns, and not just let this slide.